A_TrapShot

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Update for 2.2.0:

Var2 apparently works differently, see code for details

A_TrapShot is an action which is used to shoot a projectile like a Glaregoyle – i.e.: the projectile is fired in a particular direction, rather than firing at a particular Object or point in the map.

Var1's lower 16 bits determines the Object type number of the projectile the actor will fire. This is usually expected to be an Object type with the MF_MISSILE flag (see Projectile for examples), though any Object type is technically allowed. Note that the projectile's SeeSound Object type attribute determines the sound played when spawned, and the Speed attribute determines how fast the projectile will move when fired.

Var2's lower 16 bits determines the vertical angle the projectile is fired at, measured in degrees: 0° is directly forward, 90° is directly upwards, 180° is directly backwards, and 270° is directly downwards. The actor's angle is used as the projectile's own horizontal firing angle.

The position the projectile is fired from can also be modified by this action – Var1's upper 16 bits determines the front/back offset, relative to the actor's center, and Var2's upper 16 bits determines the height offset, relative to the actor's bottom Z position.

Code – A_TrapShot

// Function: A_TrapShot
//
// Description: Fires a missile in a particular direction and angle rather than AT something, Trapgoyle-style!
//
// var1:
//        lower 16 bits = object # to fire
//        upper 16 bits = front offset
// var2:
//        lower 15 bits = vertical angle variable
//        16th bit:
//			- 0: use vertical angle variable as vertical angle in degrees
//			- 1: mimic P_SpawnXYZMissile
//				use z of actor minus z of missile as vertical distance to cover during momz calculation
//				use vertical angle variable as horizontal distance to cover during momz calculation
//        upper 16 bits = height offset
//
void A_TrapShot(mobj_t *actor)
{
	INT32 locvar1 = var1;
	INT32 locvar2 = var2;
	boolean oldstyle = (locvar2 & 32768) ? true : false;
	mobjtype_t type = (mobjtype_t)(locvar1 & 65535);
	mobj_t *missile;
	INT16 frontoff = (INT16)(locvar1 >> 16);
	INT16 vertoff = (INT16)(locvar2 >> 16);
	fixed_t x, y, z;
	fixed_t speed;
#ifdef HAVE_BLUA
	if (LUA_CallAction("A_TrapShot", actor))
		return;
#endif

	x = actor->x + P_ReturnThrustX(actor, actor->angle, FixedMul(frontoff*FRACUNIT, actor->scale));
	y = actor->y + P_ReturnThrustY(actor, actor->angle, FixedMul(frontoff*FRACUNIT, actor->scale));

	if (actor->eflags & MFE_VERTICALFLIP)
		z = actor->z + actor->height - FixedMul(vertoff*FRACUNIT, actor->scale) - FixedMul(mobjinfo[type].height, actor->scale);
	else
		z = actor->z + FixedMul(vertoff*FRACUNIT, actor->scale);

	CONS_Debug(DBG_GAMELOGIC, "A_TrapShot: missile no. = %d, front offset = %d, vertical angle = %d, z offset = %d\n",
		type, frontoff, (INT16)(locvar2 & 65535), vertoff);

	missile = P_SpawnMobj(x, y, z, type);

	if (actor->eflags & MFE_VERTICALFLIP)
		missile->flags2 |= MF2_OBJECTFLIP;

	missile->destscale = actor->scale;
	P_SetScale(missile, actor->scale);

	if (missile->info->seesound)
		S_StartSound(missile, missile->info->seesound);

	P_SetTarget(&missile->target, actor);
	missile->angle = actor->angle;

	speed = FixedMul(missile->info->speed, missile->scale);

	if (oldstyle)
	{
		missile->momx = FixedMul(FINECOSINE(missile->angle>>ANGLETOFINESHIFT), speed);
		missile->momy = FixedMul(FINESINE(missile->angle>>ANGLETOFINESHIFT), speed);
		// The below line basically mimics P_SpawnXYZMissile's momz calculation.
		missile->momz = (actor->z + ((actor->eflags & MFE_VERTICALFLIP) ? actor->height : 0) - z) / ((fixed_t)(locvar2 & 32767)*FRACUNIT / speed);
		P_CheckMissileSpawn(missile);
	}
	else
	{
		angle_t vertang = FixedAngle(((INT16)(locvar2 & 32767))*FRACUNIT);
		if (actor->eflags & MFE_VERTICALFLIP)
				vertang = InvAngle(vertang); // flip firing angle
		missile->momx = FixedMul(FINECOSINE(vertang>>ANGLETOFINESHIFT), FixedMul(FINECOSINE(missile->angle>>ANGLETOFINESHIFT), speed));
		missile->momy = FixedMul(FINECOSINE(vertang>>ANGLETOFINESHIFT), FixedMul(FINESINE(missile->angle>>ANGLETOFINESHIFT), speed));
		missile->momz = FixedMul(FINESINE(vertang>>ANGLETOFINESHIFT), speed);
	}
}

	Actions – Projectiles	[view]
A_DropMine • A_FireShot • A_LobShot • A_MissileSplit • A_MultiShot • A_NapalmScatter • A_ShootBullet • A_SplitShot • A_SuperFireShot • A_SuperTurretFire • A_TrapShot • A_TurretFire • A_TurretStop • A_VileAttack • A_VileFire • A_VileTarget • A_HoodFire

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